Abstract
During recent decades observation of climate archives has raised several questions. Concerning the mid-Pleistocene transition problem, conflicting sets of hypotheses highlight either the role of ice sheets or atmospheric carbon dioxide in causing the increase in duration and severity of ice age cycles. The role of the solar irradiance modulations in climate variability is frequently referenced but the underlying physical justifications remain most mysterious. Here, we extend the key mechanisms involving the oceanic Rossby waves in climate variability, to very long-period, multi-frequency Rossby waves winding around the subtropical gyres. Our study demonstrates that the climate system responds resonantly to solar and orbital forcing in eleven subharmonic modes. We advocate new hypotheses on the evolution of the past climate, implicating the deviation between forcing periods and natural periods according to the subharmonic modes, and the polar ice caps while challenging the role of the thermohaline circulation.
Highlights
The paleoclimate records show perfect coherence between temperature transitions and orbital forcing but with effects not proportional to the presumed causes [1,2,3,4,5,6]
From the climate archives cited in “Data”, the methodological approach aims at representing the variations in the global surface temperature as well as in the solar forcing within the contiguous bands of resonance of Gyral Rossby Waves’ (GRWs) corresponding to each subharmonic mode
The generalization of the oceanic Rossby wave theory to long-period, multi-frequency GRWs should be a breakthrough in the understanding of the evolutions of the past climate because of the straightforwardness of the answers to some pending issues
Summary
The paleoclimate records show perfect coherence between temperature transitions and orbital forcing but with effects not proportional to the presumed causes [1,2,3,4,5,6]. Nondispersive Rossby waves of very long-period (tens of thousands years) are hypothesized by lengthening while winding around the subtropical gyres, proportionally to the period, the apparent wavelength of 8-yr average period Rossby waves dragged by the wind-driven inertial recirculation. These are observed wherever the western boundary currents leave the continents to re-enter the interior flow of subtropical gyres [8]. The speed of the anticyclonically wind-driven inertial recirculation being higher than the phase velocity of cyclonically propagating GRWs, as a result of solar forcing resonances occur when half the apparent wavelength of GRWs is an integer number of times the perimeter of the gyre
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